The plan makes great sense in theory, but I'm pretty skeptical about how this deal will pan out. Based off of my IT experience, most people that I know don't use IBM's MDM solutions because they're good. 99% of the time, its because they're stuck on legacy IBM and it would be too much of a pain to move. Based on that, I can't see many businesses making the switch to iPhones and ipads just to use IBM's MDM apps.
In the past year (BYOD aside) IT professionals have figured out that they can easily get by without deploying Apple products. Most companies bought iPads during the tablet craze trend thinking that it'll increase productivity by making people be able to be productive on the go, but many many reports have come up over the past year that the "I must have a tablet" craze is mostly over and that in a lot of cases, employees have largely gravitated back to PCs, mainly because there are few scenarios (though there are some) where a tablet actually makes you more productive. It's one of the factors that has led to iPad sales dropping 16% YoY.
In addition, IBM's revenue has been going down every quarter for the past 7 quarters and they need a reason to get people to buy their products.
On the surface, this idea makes perfect sense. Two companies who are struggling in the enterprise are using their strengths to compliment each other. IBM has backend services but no hardware and Apple has hardware but basically no backend. The question isn't the logic of the deal, but whether Apple and IBM (who have very very different structures, purposes, cultures, and mentality) can successfully collaborate together.
For reference, Microsoft does what IBM is doing for Apple for the Surface, Dell, HP, and Lenovo while Dell, HP, and Lenovo do what Apple is doing for IBM.
I'm going to wait and see if companies would want to deal with two different companies for their solutions or choose Microsoft's end-to-end solution (Windows, Windows Phone, Azure, etc...)